On Mon, Dec 2, 2013 at 11:42 AM, Vlad Yasevich <vyasev...@gmail.com> wrote: > On 12/02/2013 10:45 AM, Karl Heiss wrote: >> On Mon, Dec 2, 2013 at 9:38 AM, Vlad Yasevich <vyasev...@gmail.com> wrote: >>> On 11/27/2013 11:03 PM, Sun Paul wrote: >>>> How LKSCTP select which source address to use for the INIT_ACK or >>>> HB_ACK? below is the testing result where a router is located in the >>>> middle. >>>> >>>> Before starting the application. the packet on eth1 and eth2 are >>>> >>>> eth1 >>>> 0 packets dropped by kernel >>>> [root@localhost ~]# tcpdump -i eth1 -s 0 -nn >>>> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode >>>> listening on eth1, link-type EN10MB (Ethernet), capture size 65535 bytes >>>> 11:24:14.262489 IP 12.1.1.1.2905 > 110.1.1.1.2905: sctp (1) [INIT] >>>> [init tag: 28362903] [rwnd: 102400] [OS: 16] [MIS: 16] [init TSN: 0] >>>> 11:24:14.262522 IP 110.1.1.1.2905 > 12.1.1.1.2905: sctp (1) [ABORT] >>>> 11:24:14.539486 >>>> 11:24:16.262488 IP 12.1.1.1.2905 > 110.1.1.1.2905: sctp (1) [INIT] >>>> [init tag: 29391734] [rwnd: 102400] [OS: 16] [MIS: 16] [init TSN: 0] >>>> 11:24:16.262520 IP 110.1.1.1.2905 > 12.1.1.1.2905: sctp (1) [ABORT] >>>> >>>> eth2 >>>> [root@localhost ~]# tcpdump -i eth2 -s 0 -nn >>>> tcpdump: verbose output suppressed, use -v or -vv for full protocol decode >>>> listening on eth2, link-type EN10MB (Ethernet), capture size 65535 bytes >>>> >>>> When starting the application. the packet show as below. >>>> >>>> eth1 >>>> 11:26:02.261511 IP 12.1.1.1.2905 > 110.1.1.1.2905: sctp (1) [INIT] >>>> [init tag: 26256828] [rwnd: 102400] [OS: 16] [MIS: 16] [init TSN: 0] >>>> 11:26:02.263513 IP 12.1.1.1.2905 > 110.1.1.1.2905: sctp (1) [COOKIE ECHO] >>>> 11:26:02.264518 IP 12.1.1.1.2905 > 110.1.1.1.2905: sctp (1) [HB REQ] >>>> 11:26:02.563511 IP 12.1.1.1.2905 > 110.1.1.1.2905: sctp (1) [HB REQ] >>>> >>>> eth2 >>>> 11:26:02.261604 IP 120.1.1.1.2905 > 12.1.1.1.2905: sctp (1) [INIT ACK] >>>> [init tag: 3478239387] [rwnd: 131072] [OS: 5] [MIS: 5] [init TSN: >>>> 2330749678] >>>> 11:26:02.263583 IP 120.1.1.1.2905 > 12.1.1.1.2905: sctp (1) [COOKIE ACK] >>>> 11:26:02.264548 IP 120.1.1.1.2905 > 12.1.1.1.2905: sctp (1) [HB ACK] >>>> 11:26:02.264652 IP 11.1.1.1.2905 > 120.1.1.1.2905: sctp (1) [HB REQ] >>>> 11:26:02.264705 IP 120.1.1.1.2905 > 11.1.1.1.2905: sctp (1) [HB ACK] >>>> 11:26:02.563543 IP 120.1.1.1.2905 > 12.1.1.1.2905: sctp (1) [HB ACK] >>>> >>>> From the above result, you can see that the INIT, COOKIE ECHO and >>>> HB_REQ originated from 12.1.1.1 on eth1, but the ACK (INIT_ACK, >>>> COOKIE_ACK, HB_ACK) are returned on eth2 using source address >>>> 120.1.1.1 instead of 110.1.1.1. >>>> >>>> Why LKSCTP use 120.1.1.1 as source instead of 110.1.1.1? >>>> >>>> For simple ICMP ping test, it is normal, but not for SCTP. >>>> >>>> eth1 >>>> 11:30:02.824548 IP 12.1.1.1 > 110.1.1.1: ICMP echo request, id 37178, >>>> seq 12, length 64 >>>> 11:30:02.824559 IP 110.1.1.1 > 12.1.1.1: ICMP echo reply, id 37178, >>>> seq 12, length 64 >>>> 11:30:03.825551 IP 12.1.1.1 > 110.1.1.1: ICMP echo request, id 37178, >>>> seq 13, length 64 >>>> 11:30:03.825561 IP 110.1.1.1 > 12.1.1.1: ICMP echo reply, id 37178, >>>> seq 13, length 64 >>>> >>>> eth2 >>>> 11:30:34.027687 IP 11.1.1.1 > 120.1.1.1: ICMP echo request, id 46138, >>>> seq 2, length 64 >>>> 11:30:34.027697 IP 120.1.1.1 > 11.1.1.1: ICMP echo reply, id 46138, >>>> seq 2, length 64 >>>> 11:30:35.027686 IP 11.1.1.1 > 120.1.1.1: ICMP echo request, id 46138, >>>> seq 3, length 64 >>>> 11:30:35.027694 IP 120.1.1.1 > 11.1.1.1: ICMP echo reply, id 46138, >>>> seq 3, length 64 >>>> >>>> Below is the route information >>>> #route -n >>>> Kernel IP routing table >>>> Destination Gateway Genmask Flags Metric Ref Use >>>> Iface >>>> 110.1.1.0 0.0.0.0 255.255.255.0 U 0 0 0 >>>> eth1 >>>> 120.1.1.0 0.0.0.0 255.255.255.0 U 0 0 0 >>>> eth2 >>>> >>>> # ip route show >>>> 110.1.1.0/24 dev eth1 proto kernel scope link src 110.1.1.1 >>>> 120.1.1.0/24 dev eth2 proto kernel scope link src 120.1.1.1 >>>> >>>> Since we are using iproute2, so we will have dedicate routing table >>>> per interface >>>> >>>> # ip route show table SCTP1 >>>> default via 110.1.1.254 dev eth1 >>>> >>>> # ip route show table SCTP2 >>>> default via 120.1.1.254 dev eth2 >>>> >>>> # ip rule ls >>>> 0: from all lookup local >>>> 101: from 110.1.1.1 lookup SCTP1 >>>> 102: from 120.1.1.1 lookup SCTP2 >>>> 32766: from all lookup main >>>> 32767: from all lookup default >>>> >>>> How LKSCTP select source address to reply? If we know how it works, >>>> then we may know what is going wrong. >>> >>> LKSCTP will prefer the address returned from the routing table as long >>> as it is one of the addresses that is bound by the socket and are usable >>> by the association. >>> >>> If the address returned from the route lookup is not part of the >>> association, then lksctp attempts to lookup routes using one of the >>> source addresses it has available. Usually the first lookup succeeds >>> due to the host-model implementation in linux. >>> >>> You may want to change your rule set to be destination based. Then >>> in the table associated with the rule, specify the source address >>> you want to be used. >>> >>> -vlad >> >> I have had similar qualms myself about this behavior, and I honestly >> don't know what the correct answer should be... >> >> In my opinion, shouldn't the source address "just work" for >> acknowledgements? If the spec explicitly states that the ACK should >> have a source address that matches the destination of the chunk being >> ACKed, why should someone have to configure this behavior outside of >> the SCTP stack by default? Is it a technical limitation, or is this >> done for a particular reason? I can understand needing to override >> the behavior, but why isn't the default "sane"? > > I think the results are sane, they simply may not match expectations. > SCTP spec doesn't say anything about source address selection. It > says that a response should be send back to the source of the request. > This is being done in both cases, i.e. the destination address in > INIT-ACK matches the source of the INIT. > > The spec does contain the MAY text that allows finer control of source > addresses, but lksctp doesn't seem to implement that. Whenever we've > tried, we couldn't get the generic mechanism working to please everyone, > as everyone had slightly different configurations and expectations. So > we left it to the rules engine. >
Oops! You are correct. I must have accidentally read it as a SHOULD.. ;-) Thanks for the history on previous attempts. I had always wondered about this. Karl > In this setup, it just appears that the default routing is not what you > expect. You can easily check this with 'ip route get' command. If it > is not what you want linux allows you to change that via ip rules. > > -vlad > >> >> Karl >> >>>> >>>> On Wed, Nov 27, 2013 at 8:45 PM, Neil Horman <nhor...@tuxdriver.com> wrote: >>>>> On Wed, Nov 27, 2013 at 07:10:49AM +0800, Sun Paul wrote: >>>>>> Hi Vlad >>>>>> >>>>>> Thank for your reply. If it is based on the destination IP to find the >>>>>> best route, why the problem didn't happen on single-homing sample? >>>>>> >>>>> Because You only ever use one address from NODE A (12.1.1.1) >>>>> >>>>>> In the single-homing sample that provided in the original email, both >>>>>> of the interfaces (eth1 and eth2) are presented on NODE-B during the >>>>>> test. However, the LKSCTP library know to use the interface eth1 to >>>>>> respond to the SCTP request. >>>>>> >>>>> Yes, because it does a route lookup to each of the two ip addresses to >>>>> NODE B, >>>>> and in both lookups, the route indicates that only one source address >>>>> should be >>>>> used (12.1.1.1). If you issue a ip route show command, you'll see that >>>>> routes >>>>> to both address on NODE B match on a rule that specifies the same src >>>>> address >>>>> and interface be used. >>>>> >>>>> Neil >>>>> >>>>>> - PS >>>>>> >>>>>> On Wed, Nov 27, 2013 at 7:09 AM, Sun Paul <paul...@gmail.com> wrote: >>>>>>> Hi Vlad >>>>>>> >>>>>>> Thank for your reply. If it is based on the destination IP to find the >>>>>>> best route, why the problem didn't happen on single-homing sample? >>>>>>> >>>>>>> In the single-homing sample that provided in the original email, both >>>>>>> of the interfaces (eth1 and eth2) are presented on NODE-B during the >>>>>>> test. However, the LKSCTP library know to use the interface eth1 to >>>>>>> respond to the SCTP request. >>>>>>> >>>>>>> - PS >>>>>>> >>>>>>> On Tue, Nov 26, 2013 at 11:19 PM, Vlad Yasevich <vyasev...@gmail.com> >>>>>>> wrote: >>>>>>>> On 11/25/2013 08:03 PM, Sun Paul wrote: >>>>>>>>> Hi >>>>>>>>> >>>>>>>>> we have a problem on using LKSCTP to form a 4 ways multi-homing >>>>>>>>> network. >>>>>>>>> >>>>>>>>> Configuration >>>>>>>>> - Node-A has 2 IP addresses in different subnets, known as IP-A >>>>>>>>> (eth1), >>>>>>>>> IP-B (eth2) >>>>>>>>> - Node-B has 2 IP addresses in different subnets, known as IP-X >>>>>>>>> (eth1), >>>>>>>>> IP-Y (eth2) >>>>>>>>> >>>>>>>> >>>>>>>> First of all, this is not a 4 way multi-homed network. As far as each >>>>>>>> SCTP association is concerned, it has only 2 destinations to send to >>>>>>>> so it has only 2 ways to get there. The fact that you have multiple >>>>>>>> local addresses doesn't mean that every local address can and should >>>>>>>> be used to connect to the remote. >>>>>>>> >>>>>>>>> the four way paths are shown below. >>>>>>>>> 1. IP-A (11.1.1.1) to IP-X (11.1.1.11) >>>>>>>>> 2. IP-B (12.1.1.1) to IP-Y (12.1.1.11) >>>>>>>>> 3. IP-A (11.1.1.1) to IP-Y (12.1.1.11) >>>>>>>>> 4. IP-B (12.1.1.1) to IP-X (11.1.1.11) >>>>>>>> >>>>>>>> No, actually you only have 2 paths: one to IPX and one to IP-Y. >>>>>>>> Which source address you choose is based on routing policy >>>>>>>> decisions and is outside the scope of SCTP. >>>>>>>> >>>>>>>>> >>>>>>>>> the HB/HB_ACK is normal for the paths " IP-A to IP-X" and "IP-B to >>>>>>>>> IP-Y", but it is not correct for the rest of two. >>>>>>>> >>>>>>>> Right, because linux is using a host addressing model, not an interface >>>>>>>> addressing model. SCTP stack simply finds the best source address >>>>>>>> that can be used to reach IP-X and it happens to be IP-A. So that >>>>>>>> is what it is going to use. >>>>>>>> >>>>>>>> The above explains why you are seeing what you describe below. >>>>>>>> >>>>>>>> In the end, linux SCTP implementation determines paths solely based >>>>>>>> on the destination address. >>>>>>>> >>>>>>>> -vlad >>>>>>>> >>>>>>>>> >>>>>>>>> First of all, we are using iproute2 to form 2 table such that when >>>>>>>>> IP-B arrives on IP-X, it will know how to route back to IP-B on the >>>>>>>>> same interface, i.e (eth1). Same logic for the path "IP-A to IP-X". >>>>>>>>> >>>>>>>>> What we observed here is that when 12.1.1.1 sends INIT to 11.1.1.11, >>>>>>>>> LKSCTP will send back the INIT_ACK to 12.1.1.1 using 12.1.1.11 but not >>>>>>>>> using the IP 11.1.1.11. >>>>>>>>> >>>>>>>>> The above operation makes the subsequence HB/HB_ACK in using wrong IP >>>>>>>>> address. >>>>>>>>> >>>>>>>>> TCP trace on eth1 >>>>>>>>> 18:02:41.058640 IP 12.1.1.1.2905 > 11.1.1.11.2905: sctp (1) [INIT] >>>>>>>>> [init tag: 19933036] [rwnd: 102400] [OS: 16] [MIS: 16] [init TSN: 0] >>>>>>>>> 18:02:41.061634 IP 12.1.1.1.2905 > 11.1.1.11.2905: sctp (1) [COOKIE >>>>>>>>> ECHO] >>>>>>>>> 18:02:41.062642 IP 12.1.1.1.2905 > 11.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>> 18:02:41.062846 IP 11.1.1.11.2905 > 11.1.1.1.2905: sctp (1) [HB ACK] >>>>>>>>> 18:02:41.361811 IP 11.1.1.11.2905 > 11.1.1.1.2905: sctp (1) [HB ACK] >>>>>>>>> 18:02:41.661791 IP 11.1.1.11.2905 > 11.1.1.1.2905: sctp (1) [HB ACK] >>>>>>>>> 18:02:41.961791 IP 11.1.1.11.2905 > 11.1.1.1.2905: sctp (1) [HB ACK] >>>>>>>>> >>>>>>>>> TCP trace on eth2 >>>>>>>>> 18:02:41.058755 IP 12.1.1.11.2905 > 12.1.1.1.2905: sctp (1) [INIT ACK] >>>>>>>>> [init tag: 424726157] [rwnd: 131072] [OS: 5] [MIS: 5] [init TSN: >>>>>>>>> 3340756356] >>>>>>>>> 18:02:41.061696 IP 12.1.1.11.2905 > 12.1.1.1.2905: sctp (1) [COOKIE >>>>>>>>> ACK] >>>>>>>>> 18:02:41.062663 IP 12.1.1.11.2905 > 12.1.1.1.2905: sctp (1) [HB ACK] >>>>>>>>> 18:02:41.062791 IP 11.1.1.1.2905 > 12.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>> 18:02:41.361777 IP 11.1.1.1.2905 > 12.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>> 18:02:41.661772 IP 11.1.1.1.2905 > 12.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>> 18:02:41.961772 IP 11.1.1.1.2905 > 12.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>> 18:02:42.161771 IP 11.1.1.1.2905 > 12.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>> 18:02:42.461770 IP 11.1.1.1.2905 > 12.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>> 18:02:42.675770 IP 11.1.1.1.2905 > 12.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>> >>>>>>>>> >>>>>>>>> If we are using single homing, there is no problem on the SCTP >>>>>>>>> communication. Below is the TCP trace on eth1 using sctp_test >>>>>>>>> >>>>>>>>> 18:09:55.356727 IP 12.1.1.1.2905 > 11.1.1.11.2905: sctp (1) [INIT] >>>>>>>>> [init tag: 32516609] [rwnd: 102400] [OS: 16] [MIS: 16] [init TSN: 0] >>>>>>>>> 18:09:55.356811 IP 11.1.1.11.2905 > 12.1.1.1.2905: sctp (1) [INIT ACK] >>>>>>>>> [init tag: 3168861995] [rwnd: 131072] [OS: 10] [MIS: 16] [init TSN: >>>>>>>>> 1877695021] >>>>>>>>> 18:09:55.357727 IP 12.1.1.1.2905 > 11.1.1.11.2905: sctp (1) [COOKIE >>>>>>>>> ECHO] >>>>>>>>> 18:09:55.357788 IP 11.1.1.11.2905 > 12.1.1.1.2905: sctp (1) [COOKIE >>>>>>>>> ACK] >>>>>>>>> 18:09:55.358724 IP 12.1.1.1.2905 > 11.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>> 18:09:55.358740 IP 11.1.1.11.2905 > 12.1.1.1.2905: sctp (1) [HB ACK] >>>>>>>>> 18:09:55.379715 IP 12.1.1.1.2905 > 11.1.1.11.2905: sctp (1) [DATA] >>>>>>>>> (B)(E) [TSN: 0] [SID: 0] [SSEQ 0] [PPID 0x3] >>>>>>>>> 18:09:55.379735 IP 11.1.1.11.2905 > 12.1.1.1.2905: sctp (1) [SACK] >>>>>>>>> [cum ack 0] [a_rwnd 131064] [#gap acks 0] [#dup tsns 0] >>>>>>>>> 18:09:55.657716 IP 12.1.1.1.2905 > 11.1.1.11.2905: sctp (1) [HB REQ] >>>>>>>>> 18:09:55.657732 IP 11.1.1.11.2905 > 12.1.1.1.2905: sctp (1) [HB ACK] >>>>>>>>> >>>>>>>>> From the observations, it seems that the LKSCTP library is not able to >>>>>>>>> use the original local address when multi-homing is being used. Is >>>>>>>>> there anyway can be resolved it? >>>>>>>>> >>>>>>>>> Thanks >>>>>>>>> >>>>>>>>> PS >>>>>>>>> -- >>>>>>>>> To unsubscribe from this list: send the line "unsubscribe linux-sctp" >>>>>>>>> in >>>>>>>>> the body of a message to majord...@vger.kernel.org >>>>>>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>>>>>>>> >>>>>>>> >>>>>> -- >>>>>> To unsubscribe from this list: send the line "unsubscribe linux-sctp" in >>>>>> the body of a message to majord...@vger.kernel.org >>>>>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>>>>> >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-sctp" in >>> the body of a message to majord...@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
